Timing and Phasing for Tight Urban Diamond Interchanges

Timing and Phasing for Tight-Urban Diamond Interchanges

Stuart Samberg, P.E., PTOEVASITE Annual Meeting – June 30, 2016

Timing and Phasing for Tight Urban Diamond Interchanges

Agenda

• What is a Tight Urban Diamond

• Traditional Diamond Interchange Phasing

• Tight Urban Diamond Phasing

• Route 250 / McIntire Road Project

• Lessons Learned

• Guidance

• Conclusions

Timing and Phasing for Tight Urban Diamond Interchanges

What is a Tight Urban Diamond Interchange

• Defined by Federal Highway as an interchange with typicalintersection spacing between 200 and 400 feet

• Utilized in constrained, urban areas and requires retaining walls

• From the Alternatives Intersections/Interchanges: InformationalReport:

“The key operational aspect of a TUDI is signal coordination toensure efficient progression of traffic and minimum storage ofvehicles between the terminals.”

Timing and Phasing for Tight Urban Diamond Interchanges

Traditional Diamond Interchange – Three Phase Strategy

• Equal Ramp Phases

• Balanced Demand

• Sufficient Storage

Timing and Phasing for Tight Urban Diamond Interchanges

Traditional Diamond Interchange – Four Phase Strategy

• Conforms to Drivers’ Expectancy

• Minimizes Internal Queuing

• Progression

Timing and Phasing for Tight Urban Diamond Interchanges

Traditional Diamond Interchange – Separate Intersection

Timing and Phasing for Tight Urban Diamond Interchanges

Tight Urban Diamond Phasing

Timing and Phasing for Tight Urban Diamond Interchanges

Route 250 / McIntire Road Project - Charlottesville

• 2 Tight Diamond Interchanges (McIntire Road and Park Street)

• Design Challenges• Directional Flow• Lack of Integrated Network• Original vs. Constructed Design• Sight Distance

• Timings• Storage Distance• Grades• Clearance Intervals• Number of Phases

Timing and Phasing for Tight Urban Diamond Interchanges

Route 250 at Park Street - Simulation

Timing and Phasing for Tight Urban Diamond Interchanges

Lessons Learned

• Single Controller

• Driver Expectations

• Storage Distance

• Permissive v. Protected Phasing

Timing and Phasing for Tight Urban Diamond Interchanges

Guidance

• NCHRP 812 – Signal Timing Manual, 2nd Edition (2015)

• ITE Traffic Signal Timing Manual (2009)

• TTI Traffic Signal Operations Handbook, 2nd Edition (2011)

• TTI Signal Design Manual for Diamond Interchanges (2000)

Timing and Phasing for Tight Urban Diamond Interchanges

Conclusions

• Avoid Internal Stacking

• Balanced Timings

• Combine Engineering Approaches

• Single Controller Operation

• Understand Driver Expectancy

• Evaluate Network Impacts

Timing and Phasing for Tight Urban Diamond Interchanges

Thank you!

Questions?